As an image display device substitutable for liquid crystal display (LCD), image display devices with the use of technology such as an electrophoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method are proposed.
As for these image display device, it is conceivable as inexpensive visual display device of the next generation from a merit having wide field of vision close to normal printed matter, having smaller consumption with LCD, spreading out to a display for portable device, and an electronic paper is expected. Recently, electrophoresis method is proposed that microencapsulate dispersion liquid made up with dispersion particles and coloration solution and dispose the liquid between faced substrates.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking imaging repetition stability, because particles with high specific gravity of titanium oxide is scattered within solution of low specific gravity, it is easy to subside, difficult to maintain a stability of dispersion state. Even in the case of microencapsulating, cell size is diminished to a microcapsule level in order to make it hard to appear, however, an essential problem was not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method wherein electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution is proposed. [The Imaging Society of Japan “Japan Hardcopy '99” (Jul. 21-23, 1999) Transaction Pages 249-252] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly dissipate charges from the electro-conductive particles, and thus there is a drawback on the lack of stability.
Further, as one method of solving various problems mentioned above, it is known an image display device which comprises an image display panel, in which two or more groups of particles having different colors and different charge characteristics are sealed between two substrates, at least one of two substrates being transparent, and, in which the particles, to which an electrostatic field produced by a pair of electrodes having different potentials is applied, are made to move by means of Coulomb's force so as to display an image. In addition, it is known an image display device which comprises an image display panel, in which the liquid powders, which indicate a high fluidity in an aerosol state such that solid-like substances are suspended in a gas stably as dispersoid, are sealed between opposed two substrates, at least one of two substrates being transparent, and, in which the liquid powders, to which an electrostatic field produced by a pair of electrodes provided on one substrate or both substrates respectively is applied, are made to move so as to display an image.
In the image display devices mentioned above, in order to generate an electrostatic field between a pair of electrodes provided on the substrate, it is necessary to transmit a drive signal to the paired electrodes. Therefore, it is necessary to arrange a chip for transmitting the drive signal near the substrate. That is to say, as shown in FIG. 11, TCP (Tape Carrier Package) 53 for mounting a chip (not shown) is arranged to an end portion of a transparent substrate 52 on which a plurality of display electrodes 51 are provided. In addition, TCP 56 is arranged to an edge portion of an opposed substrate 55 on which a plurality of opposed electrodes 54 intersecting with the display electrodes 51 at right angles are provided. Then, the drive signal is controlled by the chips arranged to the TCP's 53, 56.
Therefore, in the image display device mentioned above, when the image display panel is constructed by stacking the transparent substrate 52 and the opposed substrate 55 in such a manner that the display electrodes 51 are opposed to the opposed electrodes 54 as shown in FIG. 11, it is necessary to form a frame portion to which TCP's 53, 56, that are not contributed to an image display, are connected. In this embodiment, there is a drawback such that it is not possible to achieve a compact size and a narrow frame, which are highly required for the image display device recently (Task to be solved by a first aspect of the invention).
Moreover, in the image display device mentioned above, it is possible to perform an image display, which can achieve rapid response rate due to a dry type display, simple construction, inexpensive cost and excellent stability, but it is not possible to display an image on a rear surface thereof due to its construction. In this embodiment, there is a drawback such that it is not possible to obtain the image display device enables to display an image on both surfaces of the image display panel, which are highly required for achieving a high performance image display (Task to be solved by a second aspect of the invention).